Human papillomavirus (HPV) is a member of the papillomaviridae, a group of small DNA viruses that infect a variety of higher vertebrates. More than 80 types of HPVs have been identified. Of these, more than 30 can infect the genital tract. Some types, generally types 6 and 11, may cause genital warts, which are typically benign and rarely develop into cancer. Other strains of HPV, “cancer-associated”, or “high-risk” types, can more frequently lead to the development of cancer. The primary mode of transmission of these strains of HPV is through sexual contact.
The main manifestations of the genital warts are cauliflower-like condylomata acuminata that usually involve moist surfaces; keratotic and smooth papular warts, usually on dry surfaces; and subclinical “flat” warts, which are found on any mucosal or cutaneous surface (Handsfield, H., Am. J. Med. 102(5A): 16-20, 1997). These warts are typically benign but are a source of inter-individual spread of the virus (Ponten, J. & Guo, Z., Cancer Surv. 32:201-29, 1998). At least three HPV strains associated with genital warts have been identified: type 6a (see, e.g., Hofmann, K. J., et al., Virology 209(2):506-518, 1995), type 6b (see, e.g., Hofmann et al., supra) and type 11 (see, e.g., Dartmann, K. et al., Virology 151(1):124-130, 1986).
Cancer-associated HPVs have been linked with cancer in both men and women; they include, but are not limited to, HPV-16, HPV-18, HPV-31, HPV-45, HPV-33 and HPV-56. Other HPV strains, including types 6 and 11 as well as others, e.g., HPV-5 and HPV-8, are less frequently associated with cancer. The high risk types are typically associated with the development of cervical carcinoma and premalignant lesions of the cervix in women, but are also associated with similar malignant and premalignant lesions at other anatomic sites within the lower genital or anogenital tract. These lesions include neoplasia of the vagina, vulva, perineum, the penis, and the anus. HPV infection has also been associated with respiratory tract papillomas, and rarely, cancer, as well as abnormal growth or neoplasia in other epithelial tissues. See, e.g. VIROLOGY, 2ND ED, Fields et al., Eds. Raven Press, New York, 1990, Chapters 58 and 59, for a review of HPV association with cancer.
The HPV genome consists of three functional regions, the early region, the late region, and the “long control region”. The early region gene products control viral replication, transcription and cellular transformation They include the HPV E1 and E2 proteins, which play a role in HPV DNA replication, and the E6 and E7 oncoproteins, which are involved in the control of cellular proliferation. The late region include the genes that encode the structural proteins L1 and L2, which are the major and minor capsid proteins, respectively. The “long control region” contains such sequences as enhancer and promoter regulatory regions.
HPV expresses different proteins at different stages of the infection, for example early, as well as late, proteins. Even in latent infections, however, early proteins are often expressed and are therefore useful targets for vaccine-based therapies. For example, high-grade dysplasia and cervical squamous cell carcinoma continue to express E6 and E7, which therefore can be targeted to treat disease at both early and late stages of infection.
Treatment for HPV infection is often unsatisfactory because of persistence of virus after treatment and recurrence of clinically apparent disease is common. The treatment may require frequent visits to clinics and is not directed at elimination of the virus but at clearing warts. Because of persistence of virus after treatment, recurrence of clinically apparent disease is common.
Thus, a need exists for an efficacious vaccine to both prevent and treat HPV infection and to treat cancer that is associated with HPV infection. Effective HPV vaccines would be a significant advance in the control of sexually transmissable infections and could also protect against clinical disease, particularly cancers such as cervical cancer. (see, e.g., Rowen, P. & Lacey, C., Dermatologic Clinics 16(4):835-838, 1998).
Virus-specific, human leukocyte antigen (HLA) class I-restricted cytotoxic T lymphocytes (CTL) are known to play a major role in the prevention and clearance of virus infections in vivo (Oldstone et al., Nature 321:239, 1989; Jamieson et al., J. Virol. 61:3930, 1987; Yap et al, Nature 273:238, 1978; Lukacher et al., J. Exp. Med. 160:814, 1994; McMichael et al., N. Engl. J. Med. 309:13, 1983; Sethi et al., J. Gen. Virol. 64:443, 1983; Watari et al., J. Exp. Med. 165:459, 1987; Yasukawa et al., J. Immunol. 143:2051, 1989; Tigges et al., J. Virol. 66:1622, 1993; Reddenhase et al., J. Virol. 55:263, 1985; Quinnan et al., N. Engl. J. Med. 307:6, 1982). HLA class I molecules are expressed on the surface of almost all nucleated cells. Following intracellular processing of antigens, epitopes from the antigens are presented as a complex with the HLA class I molecules on the surface of such cells. CTL recognize the peptide-HLA class I complex, which then results in the destruction of the cell bearing the HLA-peptide complex directly by the CTL and/or via the activation of non-destructive mechanisms e.g., the production of interferon, that inhibit viral replication.
Virus-specific T helper lymphocytes are also known to be critical for maintaining effective immunity in chronic viral infections. Historically, HTL responses were viewed as primarily supporting the expansion of specific CTL and B cell populations; however, more recent data indicate that HTL may directly contribute to the control of virus replication. For example, a decline in CD4+ T cells and a corresponding loss in HTL function characterize infection with HIV (Lane et al., New Engl. J. Med. 313:79, 1985). Furthermore, studies in HIV infected patients have also shown that there is an inverse relationship between virus-specific HTL responses and viral load, suggesting that HTL plays a role in viremia (see, e.g., Rosenberg et al., Science 278:1447, 1997).
The development of vaccines with prophylactic and therapeutic efficacy against HPV is ongoing. Early vaccine development was hampered by the inability to culture HPV. With the introduction of cloning techniques and protein expression, however, some attempts have been made to stimulate humoral and CTL response to HPV (See, e.g., Rowen, P. & Lacey, C., Dermatologic Clinics 16(4):835-838 (1998)). Studies to date, however, have been inconclusive.
Activation of T helper cells and cytotoxic lymphocytes (CTLs) in the development of vaccines has also been analyzed. Lehtinen, M., et al. for instance, has shown that some peptides from the E2 protein of HPV type 16 activate T helper cells and CTLs (Biochem. Biophys. Res. Commun. 209(2):541-6 (1995). Similarly, Tarpey et al, has shown that some peptides from HPV type 11 E7 protein can stimulate human HPV-specific CTLs in vitro (Immunology 81:222-227 (1994)) and Borysiewicz et al. have reported a recombinant vaccinia virus expressing HPV 16 and HPV 17 E6 and E7 that stimulated CTL responses in at least one patient (Lancet 347:1347-1357, 1996).
The epitope approach, as we have described, allows the incorporation of various antibody, CTL and HTL epitopes, from various proteins, in a single vaccine composition. Such a composition may simultaneously target multiple dominant and subdominant epitopes and thereby be used to achieve effective immunization in a diverse population.
The information provided in this section is intended to disclose the presently understood state of the art as of the filing date of the present application. Information is included in this section which was generated subsequent to the priority date of this application. Accordingly, information in this section is not intended, in any way, to delineate the priority date for the invention.